Whales and dolphins are nature's supreme vocalists. The mighty sperm whale produces deafening clicks in its blowhole which it uses to locate giant squid two miles down in the ocean abyss; while migrating narwhals use similar sounds to pinpoint vital breathing holes in Arctic ice-floes. One group of bottlenose dolphins in Brazil has even learned to communicate with fishermen in a unique partnership. But the most famous and mysterious voice of all the Ocean Giants surely belongs to male humpback whales whose haunting operatic performances may last several hours and seem to be about singing purely for the sheer pleasure of making music. Voices of the Sea reveals a surprising underwater world where sound takes the place of sight.